JP4801626B2 - Outline enhancement device - Google Patents

Description

  The present invention relates to a contour enhancement device for performing contour enhancement on an image obtained by an imaging device such as an endoscope scope.

In general, an image signal obtained by an imaging element such as an endoscope scope is displayed on a monitor or the like after being subjected to contour enhancement in order to enhance the feature of the image. Edge enhancement is performed by second-order differentiation using, for example, a Laplacian filter as described in Patent Document 1, and luminance signals of pixels having a relatively large luminance difference from the surrounding pixels are relatively greatly enhanced. Thus, the outline of the object to be photographed is clarified and displayed.
Japanese Patent No. 2918162

  However, the contour enhancement emphasizes the luminance signals of all the pixels having different luminance differences from the surrounding pixels, so that not only the contour of the object to be photographed but also noise is emphasized and displayed.

  In particular, an imaging device mounted on an endoscope scope has recently been increased in the number of pixels, and there is a tendency that minute random noise generated in units of pixels increases. Noise tends to be amplified. Therefore, when the edge enhancement is simply applied to the luminance signal by second-order differentiation as in the prior art, minute random noise is emphasized, giving the impression that the entire image is rough.

  Therefore, the present invention has been made in view of such a problem, and provides an edge emphasizing device that can perform edge emphasis without emphasizing random noise even in an image with a high pixel count. For the purpose.

  An outline emphasizing device according to the present invention includes a noise removal unit that generates a noise removal signal of a pixel of interest using a luminance signal of the pixel of interest and a first peripheral pixel located around the pixel of interest in a minute region, Edge enhancement means for detecting a wide edge component of the pixel of interest using a luminance signal of a second peripheral pixel located around the pixel of interest in a wide area wider than the pixel and the minute area, a noise removal signal, and a wide edge component And adding means for generating a processed luminance signal of the target pixel.

  The noise removal signal detects the minute range edge component of the target pixel using the luminance signal of the target pixel and the first peripheral pixel, and subtracts the minute range edge component from the luminance signal of the target pixel to generate the noise removal signal. It is preferable to do. Further, the wide range edge component and the minute range edge component are detected by, for example, second order differentiation.

  The contour emphasizing method according to the present invention includes a noise removal step for generating a noise removal signal of a target pixel using a luminance signal of the target pixel and a first peripheral pixel located around the target pixel in a minute region, An edge enhancement step of detecting a wide edge component of the pixel of interest using a luminance signal of a second peripheral pixel located around the pixel of interest in a wide area wider than the pixel and the micro area, a noise removal signal, and a wide edge component; And an adding step for generating a processed luminance signal of the target pixel.

  In the present invention, the edge is emphasized by referring to the luminance signal of a wide range of pixels, and each luminance signal is emphasized without enhancing the noise component by removing the noise by referring to the luminance signal of the pixel in the minute range. Edge enhancement can be performed.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows an endoscope system including an image contour emphasizing apparatus according to an embodiment of the present invention. The endoscope system includes a scope 10 and a processor 20. The scope 10 is an imaging device for obtaining an image signal from a subject, and the processor 20 is an image processing device for processing the image signal obtained by the scope 10 and outputting it as an observation image.

  The scope 10 includes an image sensor 11. The image sensor 11 forms an image with light from a subject, and an analog image signal is generated from the formed image. In the image sensor 11, the timing generator 16 controls the reading / reading timing of the image signal.

  The analog image signal is converted into a digital signal by an AFE (analog front end) 12, and then color interpolation is performed by a color interpolation block 13. The analog image signal subjected to the color interpolation is subjected to matrix conversion in the matrix conversion block 14 and input to the YC conversion block 15 as an RGB signal. The RGB signal is converted into a luminance signal Y and color difference signals Cb and Cr in the YC conversion block 15. The luminance signal Y and the color difference signals Cb and Cr are sent to the processor 20.

  The processor 20 has a CPU 21, and the operation of each block in the processor 20 is controlled by the CPU 21. The luminance signal Y and the color difference signals Cb and Cr sent to the processor 20 are subjected to removal of color noise by an LPF (low-pass filter) or the like in the noise removal block 22, and then the luminance signal Y is described later in the contour enhancement block 23. Edge enhancement is applied. The color difference signals Cb and Cr are not subjected to edge enhancement in the edge enhancement block 23.

  The color difference signals Cb and Cr and the luminance signal Y subjected to edge enhancement are converted into RGB signals by the RGB conversion block 24. The RGB signal is adjusted in color according to the output device in the color management block 26 after the image size is adjusted in the scale adjustment block 25 and is output as an observation image to the monitor 27 or the printer 28.

  FIG. 2 is a block diagram showing details of the contour emphasis block 23. The contour emphasis block 23 includes a first line memory block 41, a first filter 31 and a noise removing unit 33 including a subtractor 32, an edge emphasizing unit 35 including a second line memory block 42 and a second filter 34, And an adder 36. In the contour enhancement block 23, the luminance signal Y is input to both the noise removal unit 31 and the edge enhancement unit 35. In the following description, the luminance signal Y input to the contour enhancement block 23 is the input luminance signal Y0, and the luminance signal Y subjected to edge enhancement in the contour enhancement block 23 is processed luminance signal Y ′. Will be described.

  In the noise removing unit 33, the input luminance signal Y0 is sequentially input to the first line memory block 41 and the subtracter 32 for each pixel. The first line memory block 41 temporarily stores the input luminance signal Y0 for at least three lines so that the input luminance signal Y0 in the 3 × 3 region can be input to the first filter 31 at the same time.

  The input luminance signal Y0 of each pixel (target pixel P0) and the first peripheral pixel P1 located around the target pixel P0 is sequentially input to the first filter 31 from the first line memory block 41 to the first filter 31. Is done. As shown in FIG. 3, the first peripheral pixel P1 is a pixel located around the target pixel P0 located in the 3 × 3 region (small region) R1 centered on the target pixel P0.

  The first filter 31 performs edge enhancement using the input luminance signal Y0 related to the target pixel P0 and the first peripheral pixel P1, and detects an edge component (a minute range edge component E1) of the target pixel P0. As shown in FIG. 4, the first filter 31 of the present embodiment is a Laplacian filter that performs edge enhancement using the input luminance signal Y0 of the peripheral pixel P1 located in the vertical direction and the vertical direction of the target pixel P0. The minute range edge component E1 of the pixel of interest P0 is detected by secondary differentiation.

  The minute range edge component E1 is input to the subtractor 32, and the subtractor 32 subtracts the minute range edge component E1 from the input luminance signal Y0 for each pixel of interest P0, and generates a noise removal signal F1 for each pixel of interest P0. Generated.

  The input luminance signal Y0 input to the edge enhancement unit 35 is sequentially input to the second line memory block 42 for each pixel and temporarily stored in the second line memory block 42. The second line memory block 42 stores the input luminance signal Y0 for at least five lines so that the input luminance signal Y0 in the 5 × 5 region can be input to the second filter 34 at the same time.

  The input luminance signal Y0 of each pixel (target pixel P0) and the second peripheral pixel P2 located around the target pixel P0 is sequentially input to the first filter 34 from the second line memory block 42 to the second filter 34. Is done. As shown in FIG. 5, the second peripheral pixel P2 is a pixel located around the target pixel P0 located in the 5 × 5 region (wide area) R2 centered on the target pixel P0.

  The second filter 34 performs edge enhancement using the input luminance signal Y0 of the target pixel P0 and the second peripheral pixel P2, and detects an edge component (wide-range edge component E2) of the target pixel P0. In the present embodiment, as shown in FIG. 6, the second filter 34 is a 5 × 5 Laplacian filter that performs edge enhancement, and detects a wide-range edge component E2 by secondary differentiation. The second filter 34 has a peripheral pixel P2 positioned in the vertical and horizontal directions with respect to the pixel of interest P0 in the 5 × 5 region R2, and a diagonal of the pixel of interest P0 in the 3 × 3 region centered on the pixel of interest P0. Edge enhancement is performed using peripheral pixels P2 located in all directions. As described above, the edge enhancement unit 35 performs edge enhancement using the peripheral pixel P2 positioned around the target pixel P0 in the wide area R2 wider than the minute area R1.

  The noise removal signal F1 and the wide-range edge component E2 relating to the same target pixel P0 are input to the adder 36 at the same timing, and these are added in the adder 36 to generate a processed luminance signal Y ′ for each target pixel P0. The The color difference signals Cb and Cr are input to the RGB conversion block 24 without being processed in the edge enhancement block 23, and the RGB conversion block 24 generates an RGB signal from the processed luminance signal Y ′ and the color difference signals Cb and Cr. The

  FIG. 7 shows an example of signal processing performed in the contour emphasis block 23. As shown in FIG. 7, in this example, the luminance signal Y in the image captured from the image sensor has a data component D generated based on light from the subject and a noise component N that is random noise. In FIG. 7, the data component D is composed of luminance signals of a plurality of pixels having a predetermined luminance value, and the noise component N is that the luminance value of one predetermined pixel is sharply larger than the luminance values of the other pixels, The luminance value around the pixel is formed to be smaller than 0. In the input luminance signal Y0 in FIG. 7, the signal level of the data component D is the same as the signal level of the noise component N, and is indicated by S in FIG.

  In general, the noise component N has a large luminance change in a narrow region, while the data component D has a small luminance change in a narrow region. Therefore, when edge enhancement is performed using the first filter 31 with a small reference region, the edge component of the noise component N is extracted greatly, while the edge component of the data component D is not extracted so much. That is, in the minute range edge component E1, the value of the noise component N is large, but the value of the data component D is not so large. Thereby, the noise removal signal F1 obtained by subtracting the minute range edge component E1 from the input luminance signal Y0 efficiently removes the noise component N, but the edge component DE1 of the data component D is It has not been removed so much.

  In addition, the data component D has a small luminance change in a narrow area, but the luminance change in a wide area is large. Therefore, the wide-range edge component E2 (edge component DE2) for the data component D, which is detected by the second filter 34 having a wide reference area, is compared with the minute range edge component E1 (edge component DE1) for the data component D. growing.

  That is, in the noise removal signal F1, the edge component DE1 of the data component D is removed, but the edge component DE2 detected by the second filter 34 is relatively larger than the removed edge component DE1. . Therefore, in the processed luminance signal Y ′ obtained by adding the wide-range edge component E2 to the noise removal signal F1, the luminance value of the edge portion EP of the data component D is higher than that of the input luminance signal Y0.

  The wide-range edge component E2 is an edge component detected by the second filter 34 having a wide reference area, and has a relatively small high-frequency component. That is, the amount of the noise component N in the wide-range edge component E2 is smaller than the amount of the noise component N of the minute range edge component E1 removed by the noise removing unit 33. Therefore, in the processed luminance signal Y ′ obtained by adding the wide-range edge component E2 to the noise removal signal F1, the amount of the noise component N is smaller than the amount of the noise component N in the input luminance signal Y0.

  As described above, in the present embodiment, the edge is emphasized by referring to the luminance signal of a wide range of pixels, and the noise component N is enhanced by removing the noise by referring to the luminance signal of the pixel in the minute range. Therefore, the edge enhancement of the data component D can be performed.

  Further, in endoscopic observation, generally, a portion of the body where water has accumulated is observed as a high-luminance pixel by reflection of light from a light source, and a cat's eye or blackout is observed around the high-luminance pixel. Etc. are likely to occur. However, in this embodiment, noise enhancement at the periphery of the high luminance pixel is prevented, and blackout and cat's eyes that occur around the high luminance pixel are prevented.

  In the present embodiment, a filter other than a Laplacian filter can be used as the first and second filters 31 and 34. For example, a filter for performing first-order differentiation may be used. Further, the noise removal performed by the noise removal unit is not particularly limited as long as noise can be removed using the luminance signal of the minute region R. For example, the noise may be removed by obtaining an average of the luminance signals of the target pixel P0 and the peripheral pixel P1 in the minute region R1. Alternatively, other LPFs may be used.

It is a block diagram of an endoscope system in one embodiment of the present invention. It is a block diagram which shows an outline emphasis block further in detail. It is a figure for showing the pixel in a micro field. It is a figure for showing the operator of the 1st filter. It is a figure for showing the pixel in a wide area | region. It is a figure for showing the operator of the 2nd filter. It is a figure for showing an example of the signal processing performed by an outline emphasis block.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Scope 20 Processor 23 Outline emphasis block 31 1st filter 33 Noise removal part 34 2nd filter 35 Edge emphasis part E1 Small range edge component E2 Wide range edge component F1 Noise removal signal P0 Target pixel P1 1st peripheral pixel P2 2nd peripheral pixel R1 Micro area R2 Wide area Y0 Input luminance signal Y 'Processed luminance signal

Claims (4)

A noise removal unit that generates a noise removal signal of the pixel of interest using a luminance signal of the pixel of interest and a first peripheral pixel located around the pixel of interest in a minute region;
Edge enhancement means for detecting a wide range edge component of the pixel of interest using a luminance signal of a second peripheral pixel located around the pixel of interest in a wide area wider than the pixel of interest and the micro area;
An outline emphasizing device comprising: an adding unit that adds the noise removal signal and a wide-range edge component to generate a processed luminance signal of the pixel of interest.   The noise removal signal uses a luminance signal of the target pixel and the first peripheral pixel to detect a minute range edge component of the target pixel and subtracts the minute range edge component from the luminance signal of the target pixel to generate noise. The contour enhancement apparatus according to claim 1, wherein a removal signal is generated.   3. The contour emphasizing apparatus according to claim 1, wherein at least one of the wide-range edge component and the minute range edge component is detected by second-order differentiation. 4. A noise removal step of generating a noise removal signal of the pixel of interest using a luminance signal of the pixel of interest and a first peripheral pixel located around the pixel of interest in a minute region;
An edge enhancement step of detecting a wide range edge component of the target pixel using a luminance signal of a second peripheral pixel located around the target pixel in a wide range area wider than the target pixel and the minute area;
An outline emphasizing method comprising: an adding step of adding the noise removal signal and a wide range edge component to generate a processed luminance signal of the pixel of interest.

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